Problem: Simplify the following expression: ${7(2a-2)-3(-7-a)}$
Answer: Distribute the ${7}$ into the first set of parentheses: $ {7(}\gray{2a-2}{)} - 3(-7-a) $ $ {14a-14} - 3(-7-a) $ Distribute the ${-3}$ into the parentheses: $ 14a-14 {-3(}\gray{-7-a}{)} $ $ 14a-14 + {21+3a} $ Rewrite the expression to group the ${a}$ terms and numeric terms: $ {14a + 3a} {-14 + 21}$ Combine the ${a}$ terms: $ {17a} {-14 + 21}$ Combine the numeric terms: $ {17a} + {7}$ The simplified expression is $17a+7$